Development of a protocol for genetic transformation of Malus spp

A protocol to produce transgenic shoots of Malus X domestica cv Greensleaves was optimized using two gene constructs previously used to create parthenocarpic tomato, Ino-IaaM and DefH9-IaaM. The aim was to obtain sufficient nº of transgenic shoots for in vitro multiplication, transfer to soil, grafting and testing for parthenocarpy in the next years. We investigated the effects of two modifications of a previous published protocol: 1) co-transformation with an Agrobacterium containing “VIP” genes in the gene construct and 2) two different hormones or hormone combinations. More shoot regeneration was obtained with a combination of three hormones (BA:NAA:TDZ) during co-cultivation instead of IBA and no co-transformation was performed using the VIP gene. For the DefH9-IaaM transgene, 21.04% regeneration was achieved for this treatment instead of 8.95% achieved with “IBA treatment” and 4.42% with the Agrobacterium co-transformation treatment. More shoot regeneration occurred with the combination of three hormones (BA:NAA:TDZ) instead of with only IBA and no co-transformation was performed using VIP gene. Experiments using Ino-IaaM confirmed the results shown for the DefH9-IaaM transgene. The regenerated shoots were multiplied in selective media containing kanamycin and roots were obtained.